Various types of closures have been devised over the last few decades. Such closures may generally be classified as threaded closures wherein the threaded closure cap screws onto external threads on a hub to connect the closure to the hub, internal closures wherein the locking member between the hub and the closure locks within an interior of the hub, and clamp-style closures wherein clamp segments clamp together a portion of the hub and a portion of the door to connect the door and the hub. Regardless of the style of the closure, a sealing member is conventionally provided for sealing the door to the hub, so that pressure within the vessel (or a partial vacuum within the vessel) is maintained to keep fluids (liquids or gases) within the pressure vessel and prevent air or other fluids from leaking into the vessel through the closed door.
Each type of closure has features which attract certain segments of the closure market to that type of closure. Different types of closure have different costs, and different connect/disconnect times are required for different closure types to disconnect the door from the hub when the pressure in the vessel is substantially atmospheric pressure. U.S. Pat. Nos. 4,387,740, 4,466,550, 4,693,278, 6,439,415, 7,036,674, 7,341,161, 7,243,685, and Publication U.S. 2009/0145904 A1 discloses various types of closures with locking members internal to the hub. U.S. Pat. No. 4,237,936 discloses a clamp-type closure with left and right side clamp segments connected at an upper and lower portion of the door. Other clamp-type closures are disclosed in U.S. Pat. Nos. 4,288,001 4,483,458, and 3,077,360. U.S. Pat. Nos. 4,157,146 and 6,561,556 discloses closure clamps which are positioned about the perimeter of the door. U.S. Pat. Nos. 4,589,566, 6,685,380, and 6,742,957 discloses various types of threaded closures. A pipe coupling clamp is disclosed in U.S. Pat. Nos. 6,050,615 and 7,883,721.
The disadvantages of the prior art are overcome by the present invention, an improved clamp-type closure is hereinafter disclosed.